This invention relates to phase-scanned radar antenna arrays or radiating phase shifters of the slot type, with periodic control of slot or coupling, and more particularly to a line source array in which the beam may be electronically scanned over a limited angular range.
Small angle electronic scanning of a radar beam is required in many surveillance applications. Such antennas have been developed by Rockwell International as described for example in an article entitled "Inexpensive Phased Array Opens Up New Radar Applications", by Richard T. Davis in Microwaves, August 1975 at pages 15 and 16. The phased array antenna disclosed therein is based on a series ferrite scan principle in which a waveguide having series connected ferrite phase shifters inserted lengthwise between each radiating element has current applied which induces a longitudinal magnetic field in the ferrite. Electronic beam scanning is effected by controlling the propagating velocity or phase shift per unit length of the ferrite loaded waveguide. See also U.S. Pat. No. 3,855,597 by R. L. Carlise for a Phase-Scanned Radiating Array.
Also of interest are two articles in Microwaves, "Beam Pointing Direction of Travelling Wave Arrays", June 1969, pages 76 et seq.; and "A Single Bit Latching Reciprocal Ferrite Phase Shifter", March 1970, pages 46 et seq.
An improved Line Source Antenna for Small Angle Electronic Beam Scanning is described in U.S. Pat. No. 4,092,647 by J. J. Borowick, B. Gelernler, N. Lipetz and R. A. Stern. It covers a line source antenna comprising a plurality of side wall, shunt slot radiatiors in a waveguide section with a non-reciprocal latching phase shifter with matching transformers located between pairs of slots. Change of the insertion phase between adjacent slots is provided by a switching wire element running centrally through the phase shifters and matching transformers along the central axis of the waveguide. A common electronic driver is coupled to a respective switching wire element to energize (latch) a selected number of the ferrite elements which are operated in sets. While this line source antenna is an improvement, in a particular example it has 14 phase shifters, each with a pair of dielectric matching transformers, resulting in 42 parts and pieces of ferrite and dielectric being fabricated and installed therein. The active ferrites in this structure encompass only a fraction of the length of the line source, thereby resulting in less than optimum efficiency.